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Electricity

I'm sure this thread will die rather quickly due to lack of interest.

Luxman said
We don't speak of the wave, we speak of the direction of the current. During the positive half cycle the current flows into one direction, during the negative half cycle into the other. So there's ONE direction change of the electrical current per cycle or Hertz.

Yes, when you disagreed with me, I figured you meant that, but I was referring to the actual wave. I should have worded it differently.

Luxman also said
And that's wrong too (sorry). You have three-phase electric power coming to your house. Between 2 phases and the neutral you have 120V, between the third phase and the neutral you have 208V and connected to two phases you have 240V.

No, we have single phase coming to our house. It's actually two opposite 120 volt phases that when combined yield 240 volts, but isn't that still 240 volts? If you place a meter across the two legs, it will read 240 volts, so regardless of the phases, the net result is 240 volts.

What you are referring to with three phase is what they use for commercial installations.(I've never heard of three phase being run to a residential home). Most newer houses (maybe 30 years old or less) have single phase running to them, like mine does. If you refer to the link you posted for me in the other thread, it mentions that.

Yes, when you disagreed with me, I figured you meant that, but I was referring to the actual wave. I should have worded it differently.

Hehe, AC means alternating current and not alternating wave direction.
So the Hertz gives the number of current direction changes, the waveform is irrelevant.

Originally Posted by dekoda

No, we have single phase coming to our house. It's actually two opposite 120 volt phases that when combined yield 240 volts, but isn't that still 240 volts? If you place a meter across the two legs, it will read 240 volts, so regardless of the phases, the net result is 240 volts.

Now here you are contradictory. First you say you have single phase coming to your house and in the next sentence you say it's two 120 V phases.

That's exactly what I said: Between two phases you have 240 V, between one phase and the neutral (or ground) you have 120 V.
So there's no conversion happening, the voltage depends on how you connect the load to the incoming cables.

Originally Posted by dekoda

What you are referring to with three phase is what they use for commercial installations.(I've never heard of three phase being run to a residential home). Most newer houses (maybe 30 years old or less) have single phase running to them, like mine does. If you refer to the link you posted for me in the other thread, it mentions that.

That's specifically US powes supply. In Luxmanland nearly all homes have a tri-phase connection. I have 3 phases coming into my house and it's not a commercial installation.
I have for example connected my cooker and my oven on 3 phases. It's much more efficient at 380 V.
They only connect homes in the US with one or two phases because it's cheaper than 3 phases.

The advantage of the higher voltage used here is the lower loss in the cables and circuits because of half the current (Ampere) needed to get the same power.
A 2 kW heater for example needs 16.7 A on a 120 V circuit and only 8.4 A on 240 V.

Due to the (low) resistance of the cables, the loss in the cables is twice as big, or you could use half as big wires to have the same effect.
That's why all transmission lines use a very high voltage to be able to transmit high power with a low current, just to limit the loss in the wires.

Luxman said
We don't speak of the wave, we speak of the direction of the current. During the positive half cycle the current flows into one direction, during the negative half cycle into the other. So there's ONE direction change of the electrical current per cycle or Hertz.

There may only be one direction change during each cycle, but there is another one at the beginning (or end) of each cycle. If you consider a string of, say, 10 cycles, there are 20 direction changes. Or 19, I suppose, if you look at the string of 10 in isolation

What you are referring to with three phase is what they use for commercial installations.(I've never heard of three phase being run to a residential home).

Three phase is sometimes used in apartment buildings, too. It can be a bugger for people moving between a house and an apartment - 240V appliances running on 208V, or vice versa.
There may be some confusion between 'delta connection' [live wire to live wire, 208V] and 'star connection' [3 live wires each connected to neutral, 240V].

We have 3-phase to the streetlevel, need a techy to connect your home to 3-phase though (they inspect your circuit for that, seems bad things happen upstream if 3-phase short-circuits).

Anyway, can someone explain to me why power-convertors to the Aussie standard are so fecked expensive? Doesn't seem to matter if I'm coming from Euro 220v or from USA 110v, converting to Aus. is expensive. Why? Is it the Hertz thing? (we're talking about single appliance convertors going for around $50 USD btw)

I figured it would be easy to go down from 220 -> 110 (i.e. use US stuff in Aus) but appearantly not??

I was snooping around and found both this thread and a few pictures and a write-up about AC vs DC

http://www.kpsec.freeuk.com/images/ac.gif
This is a AC current. It is called a sine wave. Peak to peak is where the voltage is measured.(It gets slightly more involved but if you follow the link below it is explained. This is just the simple version.) This is a single phase AC current. The top half is in one direction and the bottom half is in the opposite direction. A 240 volt wave would have another wave going opposite to the first.http://www.kpsec.freeuk.com/images/wave.gif

The frequency is measured from the 0 line between the beginning of the + wave to the ending of the - wave.

Now here you are contradictory. First you say you have single phase coming to your house and in the next sentence you say it's two 120 V phases.

That's exactly what I said: Between two phases you have 240 V, between one phase and the neutral (or ground) you have 120 V.
So there's no conversion happening, the voltage depends on how you connect the load to the incoming cables.

Lxm

I agree that it is two phases that are 180 degrees out of phase, but for some reason it's called single phase. I asked about that in college, but I don't remember the explanation. When you explained about the 240 volts, you were referring to a four wire system, that has three phases, whereas I said that here in the states, we use a three wire single phase system for residential service.

I will bow to your expertise Lux, as your background indicates that you've had a lot more experience with this type of thing. I studied electrical engineering in college, then switched to digital electronics for a few semesters. That was 30 years ago, and my electricity theory is a bit hazy these days. It's been 25 years since I've worked with electric service, so I'm probably rusty on many points.

I also remember my professor saying that the overhead lights in the classroom were turning on and off 120 times a second because of the 60 cycle (hertz) frequency, but that our eyes couldn't detect that flickering of the lights.

Last edited by Dekoda; 15th October 2007 at 11:32 AM.
Reason: After thinking about it, I realized what was actually occurring

I was snooping around and found both this thread and a few pictures and a write-up about AC vs DC

http://www.kpsec.freeuk.com/images/ac.gif
This is a AC current. It is called a sine wave. Peak to peak is where the voltage is measured.(It gets slightly more involved but if you follow the link below it is explained. This is just the simple version.) This is a single phase AC current. The top half is in one direction and the bottom half is in the opposite direction. A 240 volt wave would have another wave going opposite to the first.http://www.kpsec.freeuk.com/images/wave.gif

The frequency is measured from the 0 line between the beginning of the + wave to the ending of the - wave.

Hi Canuck! That green colored sine wave in your post shows you the peak to peak voltage. When we compare AC to DC, then we need to take into account that the AC voltage is not always at it's maximum voltage...it rises from zero volts until it reaches the peak positive voltage (let's say +120 volts for here in the US.) It's only at +120 volts for a tiny amount of time, then it drops in voltage until it reaches the peak minus voltage of -120.

If you look at the DC wave form, it's just a straight line that starts at 0 volts, then rapidly rises to it maximum voltage. In order to compare how much work can be done with both voltages, we need to compensate for the AC voltages that are not at 120 volts, so we multiply the peak voltage by .707 to achieve the RMS voltage (Root Mean Square). The RMS voltage is the amount of AC that will do the same amount of the equivalent DC. That is, a 100 peak volt AC circuit can perform the same amount of work as a 70.7 volt DC circuit.

It's easy to see that DC is more efficient than AC, but you can't transmit DC over power lines very efficiently. There is line loss due to the resistance of the wire. There is line loss with AC also, but because it's alternating, the loss is a lot less.

I also remember my professor saying that the overhead lights in the classroom were turning on and off 120 times a second because of the 60 cycle (hertz) frequency, but that our eyes couldn't detect that flickering of the lights.

Some devices, such as lamps, don't care which way the current is flowing, so they do their thing (light up, or whatever) twice per cycle.

wow

you just never know what sort of weird and wonderful shit you're likely to find here. i remember all this stuff from my physics minor in college. boring then. um....

i thought the title meant the energy that surges between people who are very aroused. you can feel it, a little like electricity and very thrilling. especially approaching climax, seems to bring skin closer and closer. wow, i love that.

Luxman said
We don't speak of the wave, we speak of the direction of the current. During the positive half cycle the current flows into one direction, during the negative half cycle into the other. So there's ONE direction change of the electrical current per cycle or Hertz.

Yes, when you disagreed with me, I figured you meant that, but I was referring to the actual wave. I should have worded it differently.

Luxman also said
And that's wrong too (sorry). You have three-phase electric power coming to your house. Between 2 phases and the neutral you have 120V, between the third phase and the neutral you have 208V and connected to two phases you have 240V.

No, we have single phase coming to our house. It's actually two opposite 120 volt phases that when combined yield 240 volts, but isn't that still 240 volts? If you place a meter across the two legs, it will read 240 volts, so regardless of the phases, the net result is 240 volts.

What you are referring to with three phase is what they use for commercial installations.(I've never heard of three phase being run to a residential home). Most newer houses (maybe 30 years old or less) have single phase running to them, like mine does. If you refer to the link you posted for me in the other thread, it mentions that.

Not sure what this thread is really about but what is above is not true for most places in the world that I know of. First voltage is meassure with reference to something, what that something is varies quite a bit as you have shown. In most parts of the world who (most civilised places, NA being the exception use 220/230/240 volts) the reference is to something called the neutral, more about what that is in a second. It is true you can connect power across phases to get different voltages, again for 220 intsallations going across the phases gives about 415 volts. Going across the phases gives about 200-220 and yes some parts that have 110v power have a third phase that gives 220ish but meassured to netural. Trinidad for example.

In Australia what the phases are and how the come to be is all in how the power is generated and distributed. See in the power station power is generated in a delata shape, think of a triangle with a wire comming off each conner. The phase in this case can only be meassure with respect to another. Because of the maner in which the magnet in the generator is turned each phases is 120 degrees out of phase with respect to each other. It is very rare for this type of power to be used anywhere as it is only really usefull to drive 3 phase motors.

The power is then sent over the transmission lines (3 of them) at high voltage, or high tension if you will to substations. Each substation drops the voltage to a lower level. At the last substation which is usually in the street and feed from 11Kva delta it is changed to a star formation using a transformer. The star has one common point which is called the netural, but each phase has a unique end. So messuring from one phase to another (in AUS) gives about 415 volts, meassuring from one phase to netural gives 240ish. Australia also uses the MEN system where the earth/ground is bonded to netural at the switch for safety reasons.

So dekota how do you know you have two 120v phases comming in to combine to make 240. Ie what was the reference you used to meassure each individually?

A rare digression :)

Originally Posted by wannadance

you just never know what sort of weird and wonderful shit you're likely to find here. i remember all this stuff from my physics minor in college. boring then. um....

i thought the title meant the energy that surges between people who are very aroused. you can feel it, a little like electricity and very thrilling. especially approaching climax, seems to bring skin closer and closer. wow, i love that.

hornier than i thought?
dancer

I thought something similar, dancer, but the thread seems to be about, well, electricity. About which I am apparently more ignorant than I imagined. As for you being hornier than you thought, how horny did you previously think you were?

So dekota how do you know you have two 120v phases comming in to combine to make 240. Ie what was the reference you used to meassure each individually?

Now what was the orginal questions?

Hi Jimmy! I know because, first, that's standard in the US in residential homes. The power coming into my house has three wires, and if I measure between the outside two wires that are running into my circuit breaker panel, I get 240 volts. If I measure between either one of the outside wires and the middle wire, I get 120 volts.

Also, if I connect my oscilloscope to one side of the 120, I can see the waveform. If I align the waveform so that it starts at zero, then connect the scope to the other side using the same wire for neutral, the waveform is inverted...that is 180 degrees out of phase.

The original question was posted in another thread, and I moved it here. I asked Jacki what type of outlet that was in a picture of her. It was different then the outlets we have in the US, and I was curious about it. Of course that also shows my mindset when you have a picture of a beautiful woman, and I notice the outlets...

Sometimes in real life, too, Lux! They make a helluva racket and then it's candle time.

I have just exhausted my knowledge of electricity...

I watched a line worker purposely explode a transformer, and it wasn't all that loud....maybe about the same as a shotgun. There must have been a problem with the transformer because he was in a bucket truck and was using some sort of long, insulated pole. He shoved the pole at the transformer, and tried to short something out. When he hit what he was aiming for, the transformer blew and shot out a large fireball.....kinda neat.

you just never know what sort of weird and wonderful shit you're likely to find here. i remember all this stuff from my physics minor in college. boring then. um....

i thought the title meant the energy that surges between people who are very aroused. you can feel it, a little like electricity and very thrilling. especially approaching climax, seems to bring skin closer and closer. wow, i love that.

hornier than i thought?
dancer

I'm impressed Dancer! The fact that you had it in college, plus that you remember it is really neat. Most women wouldn't go near a physics course, much less remember anything about it, so again, I'm impressed.

If you've ever gotten a mild electric shock, say 20 or 25 volts, then that is similar to the feeling that you mentioned. That "spark" between two people does make you feel like you've received a mild electric shock, so you're on the right track Dancer.

Hi Jimmy! I know because, first, that's standard in the US in residential homes. The power coming into my house has three wires, and if I measure between the outside two wires that are running into my circuit breaker panel, I get 240 volts. If I measure between either one of the outside wires and the middle wire, I get 120 volts.

Also, if I connect my oscilloscope to one side of the 120, I can see the waveform. If I align the waveform so that it starts at zero, then connect the scope to the other side using the same wire for neutral, the waveform is inverted...that is 180 degrees out of phase.

The original question was posted in another thread, and I moved it here. I asked Jacki what type of outlet that was in a picture of her. It was different then the outlets we have in the US, and I was curious about it. Of course that also shows my mindset when you have a picture of a beautiful woman, and I notice the outlets...

Strange system indeed. Just one Q though are you sure they two phases are 180 appart and not 120? The reason being if you have two phases at 180 appart you have no potential difference and hence 0volts when messaured across them (unless my trade theory from 15 years ago has been distored by looking at these lovley ladies here)

tako

i loved physics! and math. but not chemistry much - boring. loved literature, zoology, space science, which then was mostly van allen belts and what they do to organelles in nucleus of HeLa cells. anyone remember that cell line?. also loved nuclear physics and relativity theory progress. i knew all those early guys. also loved pure math.

face it: i love to learn stuff...always have. had a double major and 4 minors, couldn't make up my mind..

once i got knocked across a room and out cold by an amino acid analyzer (old style with slurry tubes, about as big as a car) that had a solvent leak.

and, gosh, i felt GREAT afterwards. diagnostic test for depression, i guess...

Well, apparently not, my friend, based on all of these posts! I would have to say that since I've been a member here, this is the most unusually hot thread I've ever come across. I mean that I would think it would only appeal to a very few members. In fact, after reading your introductory post, I actually thought NOBODY would be interested in this. What's next on these boards, a discussion on advanced chemistry?

Well, apparently not, my friend, based on all of these posts! I would have to say that since I've been a member here, this is the most unusually hot thread I've ever come across. I mean that I would think it would only appeal to a very few members. In fact, after reading your introductory post, I actually thought NOBODY would be interested in this. What's next on these boards, a discussion on advanced chemistry?

Speaking of chemistry, in plants does the transport tissue xylem differ from the phloem tissue by the.....hmmm, got off topic there. Actually, the whole thing got started in another thread when I saw a picture of Jacki in a bathroom. Visible in the picture was a wall outlet that had it's receptical slots in an unusual arrangement.(unusual to me). They were standard in Oz though, but I asked about them.

I always find it fascinating how diverse the knowledge is in any group of people. Here the knowledge is not only vast, but it comes from all over the world, which also gives us different perspectives on that knowledge. An old timer once told me that even at his age, he finds that he learns at least one new thing every day.

Strange system indeed. Just one Q though are you sure they two phases are 180 appart and not 120? The reason being if you have two phases at 180 appart you have no potential difference and hence 0volts when messaured across them

That's why the article I linked to in #17 says it's wrong to say "two phase".
It's more like two copies of a single phase; you can add them together.

Hi Canuck! That green colored sine wave in your post shows you the peak to peak voltage. When we compare AC to DC, then we need to take into account that the AC voltage is not always at it's maximum voltage...it rises from zero volts until it reaches the peak positive voltage (let's say +120 volts for here in the US.) It's only at +120 volts for a tiny amount of time, then it drops in voltage until it reaches the peak minus voltage of -120.

If you look at the DC wave form, it's just a straight line that starts at 0 volts, then rapidly rises to it maximum voltage. In order to compare how much work can be done with both voltages, we need to compensate for the AC voltages that are not at 120 volts, so we multiply the peak voltage by .707 to achieve the RMS voltage (Root Mean Square). The RMS voltage is the amount of AC that will do the same amount of the equivalent DC. That is, a 100 peak volt AC circuit can perform the same amount of work as a 70.7 volt DC circuit.

It's easy to see that DC is more efficient than AC, but you can't transmit DC over power lines very efficiently. There is line loss due to the resistance of the wire. There is line loss with AC also, but because it's alternating, the loss is a lot less.

That was talked about in the link I had, but I didn't want to start getting in to that because I wasn't sure who knew what posting here.